This invention relates to apparatus for detecting the presence of a single defective cell in a multi-cell storage battery of the type normally used in automotive applications and to apparatus for automatically analyzing such a battery and including apparatus for detecting the presence of a single defective cell.
There has in the past been much effort at developing apparatus for determining the condition of lead-acid storage batteries of the type normally used for starting, lighting, and ignition in the automotive field and, in particular, for determining the acceptability of such batteries for use under adverse conditions such as the starting of an automobile engine at low temperatures. It is desirable that such apparatus be as simple as possible to use and involve the exercise of a minimum amount of judgment by the operator so that it may be operated by personnel with a relatively low level of skill or experience. It is further important that such apparatus be as accurate as possible; in applications where the apparatus is used to determine the acceptability of a battery already in service to a consumer, the same apparatus is likely to be used with batteries which are both in and out of applicable warranty provisions. It is also important that the period of time required to analyze a battery not be unreasonably long and it is further desirable that the analysis be performed without first requiring the time consuming step of recharging the battery on batteries in as wide a variety of different conditions as possible.
Apparatus for automatically analyzing the condition of automotive batteries are known in the prior art. Such apparatus and various of the desideratum relevant thereto are disclosed in the U.S. patent application of C. E. Frailing and T. J. Dougherty, Ser. No. 863,925, filed Dec. 23, 1977, entitled "Automatic Battery Analyzer" and assigned to the assignee of this application, now U.S. Pat. No. 4,193,025 which issued on Mar. 11, 1980. The disclosure of that application is hereby incorporated by reference. While the apparatus shown therein represented a significant improvement over what had been known theretofore, it has now been found that further improvements on such apparatus can be made. In particular, it was found that apparatus constructed in accord with the referenced patent application can to an inconclusive result when a battery was first tested in an undesirably high percentage of cases requiring that the battery be put through a time consuming recharging operation and then tested again. Further, it was found that the accuracy of battery analyzers could be increased over that attained with apparatus constructed in accord with the referenced patent application.